In a microwave safe bowl, place water, milk and 4 tablespoons of butter together and heat enough just to melt the butter. Pour into the large bowl of an electric mixer, add salt, sugar and the mashed potatoes. Beat with your regular beater to mix well and dissolve the sugar. Add 3 1/3 cups of bread flour and beat well until a batter is formed. Let cool to lukewarm, sprinkle yeast over the batter and beat well until yeast is fully incorporated, scraping down the sides of the bowl. Change the beater to your dough hook and add the remaining 3 cups of bread flour. Beat on medium speed until a soft dough is formed. Dough will be sticky.,Carefully turn out onto a lightly floured surface and knead by hand for 5 minutes, incorporating a little more flour if needed until you have a dough soft, smooth and no longer sticky.,Grease a large bowl. Place dough smooth side down in the bowl to grease the surface. Turn the greased, smooth side up and cover with a damp tea towel. Place in a warm area to rise for about 40-45 minutes, or until double in size.,______,Bake in a preheated 375°F oven for 35-40 minutes. Loaves should be golden on top and sound hollow when tapped. Turn out onto wire racks. Brush with a small amount of melted butter and let cool.,Freezes well.